Clamp including adjustable abutment means for attaching a flexible plate to a printing cylinder

ABSTRACT

The invention provides a plate clamp for a printing cylinder in which the clamp includes an array of hooks adjustably spaced from an abutment surface so that a trailing printing plate having suitable holes near one edge may be mounted in the clamp. A further abutment surface is provided to cooperate with a plate loading tray in order that a plate being loaded from the tray strikes the further surface and is held in a position in which rotation of the cylinder causes the hooks to engage the holes of the plate and effect automatic clamping of the plate.

United States Patent [72] Inventors Francis V. Magrath; [56] References Cited Thomas George Selman. London, England UNITED STATES PATENTS Qfg' 13255 2,512.940 6/1950 Janke .1 101/4151 1.237.396 8/l9l 7 Shreffler .t 101/279 [45] Patented Feb. 2, 1971 l,967,22l 7/1934 Allen etalv l0l/4l5.l [73] Asslgnee Gestetner Lmuted 2,553,856 5/l95l Janke lOl/4l5.l und'mEngland 3151554 l0/l964 T d 101/415 1 a British Company ownsen [32] Priority June 21, 1967 Primary Examiner-William B. Penn [33] Great Britain Assistant ExaminerE. M. Coven [31 33,733 Attorney-Cushman. Darby & Cushman [54] CLAMP INCLUDING ADJUSTABLE ABUTMENT I MEANS FOR ATTACHING A FLEXIBLE PLATE T0 ABSTRACT: The invention provides a plate clamp for a printing cylinder in which the clamp includes an array of hooks adjustably spaced from an abutment surface so that a trailing printing plate having suitable holes near one edge may be mounted in the clamp. A further abutment surface is provided to cooperate with a plate loading tray in order that a plate being loaded from the tray strikes the further surface and is held in a position in which rotation of the cylinder causes the hooks to engage the holes of the plate and effect automatic clamping of the plate.

CLAMP INCLUDING ADJUSTABLE ABUTMENT MEANS FOR ATTACI-IING A FLEXIBLE PLATE TO A PRINTING CYLINDER The present invention concerns printing apparatus. and preferably but not necessarily offset lithographic printing apparatus, and provides an improved clamping plate for mounting a trailing printing plate on a cylinder.

It is known, in printing apparatus, to mount the printing plate on the printing cylinder by clamping the leading edge of the plate in contact with the cylinder and leaving the trailing edge of the plate from free from independent restraint. Thus, during operation of the apparatus, the printing plate is caused to rotate with the cylinder by means of a clamping action on its leading edge, the remainder of the plate adopting an armate configuration adjacent the surface of the cylinder. When carrying out short-run printing operations frequent changing of the printing plate is required, and thus it is desirable that release and replacement of the printing plate should be effected easily and rapidly. Furthermore, it is often necessary to blank out parts of the image on the plate by overlaying the plate with a strip of plain plate material covering the unwanted information. For example, when preparing catalogues, it is often desirable that certain copies should be complete with prices whilst others are devoid of prices, in which case the relevant column of the plate in which the price information occurs will be blanked off during certain of the printing operatrons.

In order to provide positive location of the plate with respect to the printing cylinder it has been proposed to provide printing plates having a series of holes punched adjacent the leading edge thereof, so that a clamp provided with an array of hooks can engage in the series of holes in the plate to locate the plate. According to the present invention we provide printing apparatus comprising a cylinder, a clamp extending parallel to the axis of said cylinder for clamping on to the cylinder the end of a plate having a line of holes adjacent the edge of such plate end, a longitudinally extending array of hooks positioned on said clamp to engage in said holes in a plate to be clamped, and an abutment surface positioned to engage the end edge of a plate when received on said hooks, the spacing of the abutment surface from the hooks in a direction circumferentially of the cylinder being adjustable.

Desirably the clamp is releasably attachable to the printing cylinder and may be locked in position on the cylinder by means of a plurality of pegs extending radially outwardly of said cylinder and engaging in correspondingly positioned apertures in said clamp body. Preferably a locking member on said clamp body engages one of said pegs, and at least one other of said pegs engages in an aperture having a diameter larger than that of said other peg, a grub screw being provided in association with said larger aperture and extending transversely thereof to contact said other peg, adjustment of said grub screw while said other peg is in the larger aperture causing rotation of said clamp body about the axis of said one peg. Suitably said locking member comprises a plate which may be moved transversely of the aperture within which said one peg is to engage, said plate engaging in a peripherally extending groove on said one peg to prevent movement of the peg axially of the associated aperture. In use of the apparatus a printing plate or other sheet to be mounted on the cylinder is placed with its leading edge in contact with the abutment surface and with a suitable array of holes in register with the hooks of the clamp. The leading edge of the sheet is thus held firmly by the abutment surface and the hooks since the printing plate is urged by the first part of the abutment surface in such a direction that each hook engages firmly against one side of its associated hole.

Conveniently said abutment surface is adjustable in position with respect to said hook members in that the abutment surface is formed on a bracket which is provided with slots extending transversely thereof and adapted to receive bolts which are threadedly engageable in the body of the clamp in order to accommodate sheets having different spacings between the series of holes and the leading edge. Desirably a further abutment surface is formed on the body of the clamp and extending substantially chordally of the cylinder.

Advantageously the apparatus of the invention includes a plate loading tray, releasably securable to said printing apparatus so that a printing plate or other sheet provided with a suitable array of holes adjacent and substantially parallel to an edge thereof may be fed from the plate loading tray substantially radially inwardly to contact said further abutment surface. Preferably the discharge end of said plate loading tray includes a pair of plate contacting surfaces defining a discharge aperture so that as the cylinder is rotated when the leading edge of a plate is in contact with said further abutment surface, said hooks enter the holes in the plate, the plate bends to adopt a configuration in which the leading part extends substantially peripherally of the cylinder with said leading edge adjacent to or in contact with the first abutment surface, and the trailing part of the plate is pulled through said discharge aperture in contact with both of the plate contacting surfaces and, upon passing through said discharge aperture, is bent from the radial direction to the circumferential direction.

Suitably, guiding means are also provided for lateral guiding of the printing plate with respect to the cylinder prior to the engagement of said hooks in said holes such guiding means comprising a lateral guiding surface provided on said plate loading tray to guide a plate or sheet from the tray towards the cylinder with the holes in register with the hooks.

In order that the present invention may more fully be understood the following description is given merely by way of example, reference being made to the accompanying drawings, in which:

FIG. I is a front elevational view of a plate clamp embodying the invention;

FIG. 2 is a side elevational view of the clamp of FIG. 1; and,

FIGS. 3, 4 and 5 are side elevational views illustrating three stages of assembly of a printing plate in the clamp when attached to a printing cylinder, FIG. 5 showing the plate in clamped relation.

Referring now to FIGS. 1 and 2, there is shown a plate clamp which comprises a body 1 having a hook plate 3 and an adjustable stop plate 2 attached thereto by means of screws and bolts respectively. The book plate 3 is held in position by a plurality of countersunk screws 11, omitted from FIG. 1 for the purposes of clarity, such screws threadedly engaging in the underside of the body 1 and seating in countersunk apertures in the hook plate 3. The adjustable stop plate 2, which is substantially of U-shaped cross section, extends longitudinally of the clamp and has a pair of slots 15 orientated transversely of the clamp and positioned one at each end of the stop plate. A socket-headed bolt 9 having a washer l0 threaded thereon extends through each slot 15 and threadedly engages in the front face of the clamp body 1. Thus the stop plate is adjustable in a direction transversely of the clamp by slackening of each bolt 9 and then sliding the clamp in the required direction so that the slot 15 slides transversely of the bolt shank. The stop plate may then be locked in position by retightening of each bolt 9.

The hook plate 3 has a plurality of hooks 3' spaced along its length and extending transversely of the clamp, the hooks 3 being arranged to engage in suitably formed recesses on a printing plate in a manner which will be explained more fully below.

The clamp body 1 also has a pair of apertures 16 and a central aperture 16' extending transversely of the body, such apertures being adapted to receive suitably disposed pegs on a printing cylinder. The central aperture 16' is associated with a pivotable member 5 which has a blade portion 5' and which is mounted on a pivot pin 7 extending transversely of the clamp body I. The central one of an array of three pegs 32 mounted on a boss 33 of printing cylinder (see FIG. 2) is provided with a peripherally extending groove 34 at a certain position along its length. The pivotal member 5 is shown in an operative position in FIG. I and in this position the blade portion 5' will fit into the groove 34 in the associated peg and will prevent withdrawal of the clamp from the array of pegs 32.

A helical spring 6 is seated in a recess in the clamp body I and is compressed between the lower face of the recess and an abutment face 26 of the pivotable lever 5. Thus the lever is urged for anticlockwise rotation about pivot pin 7. i.e. towards its operative position. The extreme right-hand end of the pivotal lever 5 is provided with a threaded aperture 27 into which a bolt 4 is screwed, the arrangement being such that screwing in of bolt 4 will result in anticlockwise rotation of the lever 5 about pivot pin 7. The two outer apertures 16 of the array of three are each provided with grub screws 8 for a purpose to be explained below.

In use of the clamp, the leading edge of the printing plate will be positioned in the gap between the hooks 3' and that surface I4 of the U-shaped adjustable stop member 2 which coincides with the bridge portion of the U. This surface 14 acts as an abutment during the use of the clamp. The front face of the clamp body I adjacent the abutment surface 14 is provided with a step 19 which constitutes a further abutment surface the significance of which will be explained later with reference to FIGS. 3 and 5.

FIG. 1 shows that, at the right-hand end of the clamp as viewed in FIG. 1, a lateral guide 13 is provided in the form of a surface extending transversely of the clamp.

In order to indicate the use of the clamp, reference will now be made to FIGS. 3, 4 and 5 which illustrate the process of fastening a printing plate on a printing cylinder. Referring first to FIG. 3, the plate clamp is shown fastened on a series of pegs 24 of a printing cylinder 25. The printing plate 17 to be attached to the cylinder 25 is shown mounted on a plate loading tray 21 which comprises a pair of arms 22 having hook ends adapted to engage over suitable suitably disposed studs on the printing machine, and a printing plate guide 23 for ensuring that the printing plate is accurately positioned with respect to the printing machine.

The mounting of the plate in the machine is as follows. Initially it should be ensured that the plate clamp is correctly orientated with respect to the printing cylinder 25. This is achieved by adjustment of the above-mentioned pair of grub screws 8 associated with the outer aperture 16 of the body 1.

As viewed in FIG. I if the left-hand edge of the clamp is to be raised and the right-hand end is to be lowered then the grub screw 8 nearest the right-hand end of the clamp is slackened until manual pivoting of the clamp in a clockwise direction about the center peg 24 causes contact between the lower end face of grub screw 8 at the right-hand end and the peg 24 associated with such screw. Once this situation has been reached the left-hand grub screw 8 is tightened until it bears against its own associated peg 24. Once both grub screws are in contact with their respective pegs the clamp should be checked to ensure that the orientation is in fact correct and, if no further adjustment is required, the clamp is then ready for use.

FIG. 3 illustrates the method by which the plate loading tray 21 is clipped on to the printing machine, namely by means of hook-ended arms 22, and shows clearly the position of a printing plate on the tray.

Before moving the printing plate towards the printing cylinder, i.e. before the FIG. 3 position of the plate is reached, the printing cylinder is rotated until it reaches the orientation shown in FIG. 3, whereupon a spring detent arrangement (not shown) will hold the cylinder in the desired plate loading position.

The printing plate I7 is then slid towards the printing cylinder with a lateral edge in contact with one of the side arms 22 serving as a lateral guide, until the leading edge 18 of the printing plate 17 abuts the surface 19 adjacent the step in the front face of the clamp body I. The plate is pusheduntil the leading edge 18 becomes securely wedged between surface 19 and abutment surface 14 of the adjustable stop plate 2.

The following description assumes that the adjustable stop plate 2 is correctly positioned for the particular spacing. between leading edge 18 and array of holes in the printing plate. Once the plate leading edge 18 has reached the limit of its leftward travel the printing cylinder 25 must be rotated in a an anticlockwise direction so that the hooks 3 rise and enter the holes 20 of the printing plate 17. and soon the shoulder 28 of the printing cylinder rises to abut the underside of the printing plate as shown in FIG. 4. Upon further rotation of the printing cylinder the movement of shoulder 28 will tend to lift the printing plate 17 upwardly. However, the left-hand edge 29 of the plate guide 23 exerts a downward force on the plate I7 at a position to the right of the point of contact between shoulder 28 and plate I7, thereby causing a clockwise bending moment to be experienced by the plate 17. This bending moment, when resisted by the natural rigidity of the printing plate, will cause a certain drag on the plate which will resist the tendency of the plate to slide out from the plate loading tray 21. Thus the hooks 3' will tend to engage the edges of the holes 20 nearest the leading edge of the plate (i.e. the edges 30 in FIG. 3) and will then pull the printing plate from the tray 21.

Another result of the clockwise bending moment on the plate 17 will be that the leading edge 18 will tend to rise onto the abutment surface 14. This motion is further assisted by the fact that the hooks 3' have risen in contact with the edges 30 of the holes 20 and there will be a tendency for the leading edge 18 of the plate to withdraw from its initial wedged position. In so withdrawing, and in suffering the tendency to rise onto the abutment surface 14, the leading edge 18 will in fact traverse the abutment surface 14 until it arrives at the position illustrated in FIG. 4 where leading edge 18 abuts the center of the abutment surface 14.

Continued rotation of the cylinder 25 towards the position illustrated in FIG. 5 will result in the plate 17 being wrapped around the cylinder 25 until the free trailing end of the plate leaves the plate loading tray 21. At this stage, the drag exerted by the plate loading tray 21 on the printing plate 17 is exerted on the plate trailing edge alone and the plate has adopted an arcuate in which it tends to conform with the curved surface of the cylinder 25.

If desired the hook-ended arms 22 of the plate loading tray 21 may be disengaged from the pins 31 of the printing machine and the tray 21 be disposed with during the printing operation. However, it is equally possible to run the machine with the plate loading tray in place.

It should be pointed out that, although the body clamp body I is illustrated as comprising three apertures 16, 16 and 16, it will be possible for merely two apertures to be used, one being provided with the grub screw 8 for adjustment purposes and the other being provided with the pivotable lever 5.

When it is desired to remove the clamp from the cylinder the screw 4 is at least partially withdrawn so that the lever 5 may be pivoted in a clockwise direction against the action of compression spring 6, in order that the blade portion 5 may be withdrawn from aperture 16' and permit removal of the clamp body 1 from the central peg 24 and at the same time from the two outer pegs. However, if the two grub screws 8 have been overtightened during adjustment of the orientation of the clamp, it will first become necessary to loosen the screws 8 very slightly in order to permit withdrawal of the clamp from the pegs.

As explained hereinbefore, adjustment of the position of the stop plate 2 is effected by slackening of the bolts 10 and by movement of the stop plate 2 to a fresh position in which the spacing between the abutment surface 14 and the hooks 3' corresponds to the spacing between the leading edge 18 and holes 30 of the printing plate 17. Retightening of the bolts 10 will secure the stop plate 2 in position.

Since different batches of printing plates may have a different spacing between the row of holes 30 and the leading edge 18 of the plate, the apparatus described is particularly useful in that the adjustable stop plate 2 may be reset for each batch of plates.

In use therefore, before the first plate of a batch is filled, the bolts 10 are slackened off and the stop plate 2 is moved upwardly away from the hooks 3. The first plate of the batch is then placed by hand on the cylinder 25 with the holes 30 threaded on the hooks 3' after which the adjustable stop plate 2 is moved downwardly to contact the leading edge 18 of the plate. When the bolts l0 have been tightened the trailing plate is held securely in place at its leading edge, and is prevented from movement circumferentially or axially of the cylinder 25. This adjustment step allowances both for variations in the spacing of the holes 30 from leading edge 18. and also for nonparallelism of the holes and leading edge. The remaining plates of the batch may then be fixed to the cylinder by using the plate loading tray 21.

When a new batch of plates is to be used, the resetting process is once again carried out on first plate of the batch.

Although the description above has referred throughout to the attaching of a printing plate 17 to the clamp, it is to be understood that the clamp may equally be used for mounting a blanking plate over a printing plate is already retained by the clamp.

We claim:

1. An improved printing apparatus comprising:

a plate carrying member having an axis of rotation and a cylindrical surface;

a single plate leading edge clamp mounted on said plate carrying member and extending parallel to said axis of rotation;

said clamp having an array of hooks projecting laterally to engage a suitably arranged array of holes adjacent an edge of a plate to be clamped, said array extending substantially parallel to said axis of rotation;

said clamp further comprising a plate edge abutment surface formed on said clamp and spaced from said array of hooks, the abutment surface being disposed in a plane extending substantially radially of said cylindrical surface for engaging said edge of the plate and clampingly urging said plate against the hooks to cause engagement of said hooks with said array of holes; and

means for adjusting and locking both the spacing and the angular orientation of the plate abutment surface relative to said array of hooks to permit the use of said clamp with plates having an initially misaligned array of holes with respect to said array of hooks by varying the engagement of said abutment surface and said plate edge.

2. The improved printing apparatus set forth in claim 1, wherein said clamp comprises a clamp body including said hooks, an elongate bracket including said abutment surface and extending along and securable to said body, slot means orientated transversely of said elongate bracket to extend peripherally with respect to said cylindrical surface, threaded hole means formed in the clamp body in register with said slot means and locking screw means engageable in said threaded hole means for locking said bracket with respect to said body.

3. The impioved printing apparatus as set forth in claim 1, wherein said clamp is provided with an array of aperture means extending radially with respect to said cylindrical surface, said array extending parallel to said axis of rotation; and

wherein a corresponding array of pegs extends radially outwardly from said plate carrying member for engagement with said aperture means; said aperture means each having a diameter at least as great as the diameter of an associated one of said pegs.

4. The improved printing apparatus as set fort forth in claim 3, including: a locking member on said clamp movable across one of said aperture means for locking with one of said pegs, at least one other of said pegs being receivable in one of said aperture means which has a diameter larger than that of said other of said pegs; and a grub screw extending through said clamp in a direction transversely of said other peg and engaging said other peg, whereby adjustment of said grub screw while said other peg is in said larger aperture means causes rotation of said clamp about the axis of said one peg.

5. The improved printing apparatus as set forth in claim 4, wherein said locking member comprises a plate movable transversely of an associated aperture means, said one peg having a peripherally extending groove formed thereon and engaged by said plate to prevent movement of said one peg axiallg' of said associated aperture means.

. The improved printing apparatus as set forth in claim 1,

wherein a further plate edge abutment surface is formed on said clamp adjacent the first first-mentioned plate abutment surface and extends substantially chordally of said cylindrical surface to be engaged by the leading edge of a plate being applied to said plate carrying member along a direction radially of the cylindrical surface.

7. The improved printing apparatus as set forth in claim 6, including a plate loading tray, releasable means attaching said plate loading tray to said printing apparatus, to enable a printing plate provided with a array of holes adjacent and substantially parallel to an edge thereof to be fed from the plate loading tray substantially radially inwardly to contact said further abutment surface.

8. The improved printing apparatus as set forth in claim 7, wherein said plate loading tray has a plate supporting surface and a plate guide together defining a discharge aperture, said plate supporting surface and plate guide being shaped and positioned so that during loading of a printing plate from said tray onto said clamp, the rotatable plate carrying member may be rotated when the leading edge of a plate has made contact with said further abutment surface, permitting said hooks to enter the holes in the plate, the plate adopting a configuration in which the leading part extends substantially peripherally of the cylindrical surface with said leading edge adjacent to or in contact with the first mentioned abutment surface, and the trailing part of the plate is retained by said plate guide to extend substantially radially of said cylindrical surface.

9. The improved printing apparatus set forth in claim 7, wherein a lateral guiding surface is provided on said plate loading tray to guide a plate from the tray towards the cylindrical surface with the holes in register with the hooks. 

1. An improved printing apparatus comprising: a plate carrying member having an axis of rotation and a cylindrical surface; a single plate leading edge clamp mounted on said plate carrying member and extending parallel to said axis of rotation; said clamp having an array of hooks projecting laterally to engage a suitably arranged array of holes adjacent an edge of a plate to be clamped, said array extending substantially parallel to said axis of rotation; said clamp further comprising a plate edge abutment surface formed on said clamp and spaced from said array of hooks, the abutment surface being disposed in a plane extending substantially radially of said cylindrical surface for engaging said edge of the plate and clampingly urging said plate against the hooks to cause engagement of said hooks with said array of holes; and means for adjusting and locking both the spacing and the angular orientation of the plate abutment surface relative to said array of hooks to permit the use of said clamp with plates having an initially misaligned array of holes with respect to said array of hooks by varying the engagement of said abutment surface and said plate edge.
 2. The improved printing apparatus set forth in claim 1, wherein said clamp comprises a clamp body including said hooks, an elongate bracket including said abutment surface and extending along and securable to said body, slot means orientated transversely of said elongate bracket to extend peripherally with respect to said cylindrical surface, threaded hole means formed in the clamp body in register with said slot means and locking screw means engageable in said threaded hole means for locking said bracket with respect to said body.
 3. The improved printing apparatus as set forth in claim 1, wherein said clamp is provided with an array of aperture means extending radially with respect to said cylindrical surface, said array extending parallel to said axis of rotation; and wherein a corresponding array of pegs extends radially outwardly from said plate carrying member for engagement with said aperture means; said aperture means each having a diameter at least as great as the diameter of an associated one of said pegs.
 4. The improved printing apparatus as set fort forth in claim 3, including: a locking member on said clamp movable across one of said aperture means for locking with one of said pegs, at least one other of said pegs being receivable in one of said aperture means which has a diameter larger than that of said other of said pegs; and a grub screw extending through said clamp in a direction transversely of said other peg and engaging said other peg, whereby adjustment of said grub screw while said other peg is in said larger aperture means causes rotation of said clamp about the axis of said one peg.
 5. The improved printing apparatus as set forth in claim 4, wherein said locking member comprises a plate movable transversely of an associated aperture means, said one peg having a peripherally extending groove formed thereon and engaged by said plate to prevent movement of said one peg axially of said associated aperture means.
 6. The improved printing apparatus as set forth in claim 1, wherein a further plate edge abutment surface is formed on said clamp adjacent the first first-mentioned plate abutment surface and extends substantially chordally of said cylindrical surface to be engaged by the leading edge of a plate being applied to said plate carrying member along a direction radially of the cylindrical surface.
 7. The improved printing apparatus as set forth in claim 6, including a plate loading tray, releasable means attaching said plate loading tray to said printing apparatus, to enable a printing plate provided with a array of holes adjacent and substantially parallel to an edge thereof to be fed from the plate loading tray substantially radially inwardly to contact said further abutment surface.
 8. The improved printing apparatus as set forth in claim 7, wherein said plate loading tray has a plate supporting surface and a plate guide together defining a discharge aperture, said plate supporting surface and plate guide being shaped and positioned so that during loading of a printing plate from said tray onto said clamp, the rotatable plate carrying member may be rotated when the leading edge of a plate has made contact with said further abutment surface, permitting said hooks to enter the holes in the plate, the plate adopting a configuration in which the leading part extends substantially peripherally of the cylindrical surface with said leading edge adjacent to or in contact with thE first mentioned abutment surface, and the trailing part of the plate is retained by said plate guide to extend substantially radially of said cylindrical surface.
 9. The improved printing apparatus set forth in claim 7, wherein a lateral guiding surface is provided on said plate loading tray to guide a plate from the tray towards the cylindrical surface with the holes in register with the hooks. 